Magnetic clutch

ABSTRACT

A magnetic clutch comprising a main rotating unit rotated from a driving source, a rotary shaft concentric with said main rotating unit and rotatable independent thereof and adapted to be connected to a driven member, an armature mechanically connected to said rotary shaft and placed opposite to said main rotating unit in the axial direction, said armature being movable in the axial direction to a first position separated from said main rotating unit by a predetermined distance and to a second position engageable with said main rotating unit to rotate therewith, and magnetic means for attracting said armature from the first position to the second position, wherein said armature and rotary shaft are connected to each other through the intermediary of a coupling member comprising a cylindrical elastic material concentric with said rotary shaft and having a first and second cylindrical surfaces, said first cylindrical surface being mechanically connected to said armature and said second cylindrical surface being mechanically connected to said rotary shaft, whereby the axial elastic strain produced in said coupling member at the second position of said armature produces a force which causes said armature to return to the first position.

States Patent 1 Higuchi 1 Nov. 27, 1973 [75] Inventor: Aichi-ken,

[73] Assignee: Nippondenso Co., Ltd., Kariya-shi, Aichi-ken, Japan 22 Filed: Mar. 30, 1972 21 Appl. No.: 240,877

[30] Foreign Application Priority Data 192/84 A, 84 AA, 84 AB, 84 C, 89 R, 106.1; 267/153; 64/27 NM [56] References Cited UNITED STATES PATENTS 2,927,674 3/1960 Everitt 192/107 M 3,384,213 5/1968 Bernard et al. 192/84 C 3,455,421 7/1969 Miller l92/84C 3,557,573 l/1971 Hansgen. 64/27 NM X 1,896,968 2/1933 Paton 192/70.l7 3,205,989 9/1965 Mantey... 192/84 C 3,232,077 2/1966 Binder 64/27 NM HayashL. 192/84 C Pierce 192/84 C Primary ExaminerAllan D. Herrmann Att0mey-John W. Malley et al.

[ 5 7] ABSTRACT A magnetic clutch comprising a main rotating unit rotated from a driving source, a rotary shaft concentric with said main rotating unit and rotatable independent thereof and adapted to be connected to a driven member, an armature mechanically connected to said rotary shaft and placed opposite to said main rotating unit in the axial direction, said armature being movable in the axial direction to a first position separated from said main rotating unit by a predetermined distance and to a second position engageable with said main rotating unit to rotate therewith, and magnetic means for attracting said armature from the first position to the second position, wherein said armature and rotary shaft are connected to each other through the intermediary of a coupling member comprising a cylindrical elastic material concentric with said rotary shaft and having a first and second cylindrical surfaces, said first cylindrical surface being mechanically connected to said armature and said second cylindrical surface being mechanically connected to said rotary shaft, whereby the axial elastic strain produced in said coupling member at the second position of said armature produces a force which causes said armature to return to the first position.

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27 Ila/ MAGNETIC CLUTCH FIELD OF THE INVENTION The present invention relates to magnetic clutches and more particularly to a magnetic clutch which is used, for example, to intermittently engage and disengage an automotive air-conditioning compressor with the automobile engine shaft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front view of a magnetic clutch known in the art.

FIG. 2 is a longitudinal sectional view taken along the line II II of FIG. 1.

FIG. 3 is a front view showing an embodiment of the magnetic clutch according to the present invention.

FIG. 4 is a longitudinal sectional view taken along the line IV IV' of FIG. 3.

FIG. 5 is a longitudinal sectional view of a partially modified form of the magnetic clutch shown in FIG. 4.

FIG. 6 is a front view of another embodiment of the magnetic clutch according to the present invention.

FIG. 7 is a longitudinal sectional view taken along the line VII VII of FIG. 6.

FIG. 8 is a longitudinal sectional view of a partially modified form of the magnetic clutch shown in FIG. 7.

FIG. 9 is a front view showing a further embodiment of the magnetic clutch according to the present invention.

FIG. 10 is a longitudinal sectional view taken along the line X X of FIG. 9.

FIG. 11 is a longitudinal sectional view of a partially modified form of the magnetic clutch shown in FIG. 10.

FIG. 12 is a front view showing a still further embodiment of the magnetic clutch according to the present invention.

FIG. 13 is a longitudinal sectional view taken along the line XIII XIII of FIG. 12.

FIG. 14 is a longitudinal sectional view of a partially modified form of the magnetic clutch shown in FIG. 13.

FIG. 15 is a front view showing a still further embodiment of the magnetic clutch according to the present invention.

FIG. 16 is a longitudinal sectional view taken along the line XVI XVI of FIG. 15.

FIG. 17 is a longitudinal section view of a partially modified form In known clutches of this type, as for example illustrated in FIGS. I and 2, an annular flat-shaped cushion rubber 17a is used to lessen the force of a shock applied to the compressor and three to four leaf springs 30 are disposed on the circumference of a first retaining plate 18 to which the cushion rubber is securely bonded, with one end of the leaf springs 30 being fixed securely by rivets 20a. The other ends of the leaf springs 30 are securely fixed by similar rivets 20b to an armature 16 which is attracted to a main rotating unit 8 when a current is supplied to an excitation coil 3. A second retaining plate 19 to which the cushion rubber 17a is also bonded is secured to a hub 21 by a plurality of rivets 22.

With the construction described above, when the excitation coil 3 is energized producing magnetic flux in a magnetic circuit shown by broken lines a in FIG. 2, the armature 16 is attracted to the main rotating unit 8 so that the rotation of the main rotating unit 8 is transmitted to a rotary shaft 2 of the compressor through the members including the armature l6, leaf springs 30, first retaining plate 18, flat-shaped cushion rubber 17a, second retaining plate 19 and hub 21. In this case, the impact load applied to the compressor is lessened by the torsion of the cushion rubber 17a in the rotational direction. When the excitation coil 3 is deenergized, the armature 16 is returned to its original position by the restoring force of the leaf springs 30.

A disadvantage of conventional magnetic clutches of the type constructed as described above is that the annular flat-shaped cushion rubber 17a is employed solely for the purpose of absorbing the impact load applied to the compressor and thus a plurality of the armature returning leaf springs 30 are needed to return the armature 16 to its original position making the construction more complicate and requiring more time for assemblage.

SUMMARY OF THE INVENTION In order to solve the foregoing deficiency it is therefore the object of the present invention to provide a magnetic clutch, wherein a cylindrical cushion rubber adapted to perform the function of absorbing the force of a shock in the direction of rotation and the armature returning function is provided between the armature and the hub connected to the rotary shaft on the compressor side in the rotation transmitting path of the magnetic clutch, and said cushion rubber is preliminarily provided with an elastic force which acts in the restoring direction (hereinafter referred to as an initial reaction force). Thus, the magnetic clutch according to .the present invention needs no armature returning leaf DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be explained with reference to the illustrated embodiments. Now referring first to FIGS. 3 and 4, numeral 1 designates a compressor housing; 2 a rotary shaft of the compressor; 3 an excitation coil mounted in a stator housing 4 and wound into a cylindrical form. The excitation coil 3 connected to the external power source (not shown) by lead wires 5. Numeral 6 designates a bushing through which the lead wires 5 are brought to the outside of the stator housing 4. The excitation coil 3 is securely mounted in the stator housing 4 by a frame member 7 of a molded resin. Numeral 8 designates a main rotating unit having a pulley formed as an integral part thereof. The main rotating unit 8 comprises a bearing 9, a friction plate 10, inner and outer magnetic circuit portions 11 and 12, a reinforcing connecting portion 13 connecting the inner and outer magnetic circuit portions 11 and 12 together, and a V-grooved portion 14. The bearing 9 is mounted in the compressor housing 1 and is secured to the housing 1 by a circlip 15. The inner and outer magnetic circuit portions 11 and 12 are adapted to rotate along the inner and outer peripheries of the stator housing 4. The friction plate 10 is attached to the inner and outer magnetic circuit portions 11 and 12 with a binder. Numerals 11a and 12a designate the attracting surfaces of the inner and outer magnetic circuit portions 11 and 12, respectively, which are normally placed opposite to an armature 16 and spaced away therefrom by a predetermined distance to attract the armature 16 by the magnetic force of the magnetic circuit. The attracting surfaces 11a and 12a are substantially flush with a surface a of the friction plate 10. Numeral 17 designates a cylindrical coupling member of an elastic material which is attached to a first retaining plate 18 and a second retaining plate 19 concentric therewith, the first and second retaining plates 18 and 19 being made of steel sheet formed into a bell-shape. The first retaining plate 18 is secured to the armature 16 by a plurality of rivets 20 andthe second retaining plate 19 is secured to a hub 21 by a plurality of rivets 22. The hub 21 is in turn mountedon the compressor shaft 2 by a nut 23, a spring washer 24 and so on. In this case, to provide the aforesaid predetermined distance between the armature 16 and the attracting surfaces of the main rotating unit 8, several adjust washers 25 are provided, after adjustment, between the compressor shaft 2 and the hub 21. Numeral 26 designates a flat key; 27 a belt for transmitting the rotation from the engine (not shown) to the main rotating unit 8; 28 a circlip for attaching the stator housing 4 to the compressor housing 1. Numeral29 designates pressure means consisting of a plurality of protruding portions formed in the second retaining plate 19 and stamped out toward the armature 16 thereby producing an axial strain in the elastic coupling member 17 and thus providing the first retaining plate 18 connected to the armature 16 with a force which acts toward the left in FIG. 4,i.e., an initial reaction force. In this way, the distance between the armature 16 and the attracting surfaces of the main rotating unit 8is positively ensured and thus the armature 16 and the main rotating unit 8 are normally held apart from each other.

The magnetic clutch of the present invention constructed as described above operates as follows: When a DC current is supplied to the excitation coil 3 a magnetic flux is produced as shown by the armature 16 a so that the, attracting surfaces 11a and 12a of the main rotating unit 8 attract the armature 16 and stick fast thereto. At this time, since the cylindrical coupling member 17 is deflected in the axial direction to the extent equal to the distance between the attracting surfaces of the main rotating unit 8 and the armature 16 i and since the main rotating unit 8 is being driven from the engine through the belt 27, this driving force is transmitted to the armaturel6 and hence to the coupling member 17. Up to this time the compressore has beenat rest and thus the force produced by the load and the moment of inertia of the compressor and the force by the driving force and the moment of inertia of the rotating driving parts are impulsively applied to the coupling member 17 so that the coupling member 17,

in its axially deflected state, is further twisted in the direction of rotation thereof. This action of the coupling member 17 lessens the impact force and permits the transmission of the driving force to the compressor.

When the excitation coil 3 is de-energized, the attractiveforce acting on the armature 16 collapses so that the armature 16 is returned to its original position by the restoring force of the coupling member 17 by its elasticity (the restoring force from the axial deforma- 4 tion) and the initial reaction force of the coupling member 17.

While in the embodiment described above the coupling member 17 has been described as being provided with the initial reaction force acting toward the left in FIG. 4 by the pressing means 29 consisting of a plurality of protruding portions formedin the second retaining plate 19 and stamped out toward the armature 16, a modified form of the pressing means 29 consisting of a plurality of elastic members may be disposed between the armature 16 and the second retaining plate 19 so as to provide the coupling member 17 with the required initial reaction force which acts toward left in FIG. 5 by the pressing means 29.

Referring now to FIGS. 6 and 7, another embodiment of the present invention will be explained. In the figures, identical numerals as used in FIGS. 3 and 4 designate the identical or similar parts. A coupling member 1 17 formed into a cylindrical shape is bonded to a first retaining plate 1 18 of sheet steel formed into a cylindrical shape and a second retaining plate 119 of steel sheet formed into a bell shape. In this case, the outer diameter of the cylindrical coupling member 117 is compressed by about 10 percent by the first retaining plate 118 to increase the strength of the coupling member 1 17. A portion 1 18a of the first retaining plate 1 18 is driven in the stepped inner peripheral portion of a cylindrical retaining plate mounting member 116a formed integral with an armature 116, and epoxy resin is filled in the whole space between the retaining plate mounting member 116a and the first retaining plate 118 securely bonding them together along the whole outer periphery of the first retaining plate 118 and the whole inner periphery of the retaining plate mounting member 116a. The second retaining plate 119 is also secured to the hub 21 by a plurality of the rivets 22. Numeral 29 designates pressing means consisting of a plurality of protruding portions formed in the second retaining platel 19 and stamped out toward the armature 116 thereby providing the coupling member 117 with the initial reaction force which acts towards the left in FIG. 7.

In the case of this embodiment, since the outer diameter of the coupling member 117 is compressed by about 10 percent by the first retaining plate 118 so as to increase the strength of the coupling member 117, the first retaining plate 118 is subject to the expansion stress of the coupling member 117, while as the armature 116 is attracted to the attracting surfaces 11a and 12a of the main rotating unit 8 an impact force is imparted tothe coupling member 117 so that the stress caused by this impact force is applied to the first retaining plate 118. If, in this case, these two stresses are locally applied to the first retaining plate 118, there is the danger of the retaining plate 118 breaking down. However, since the retaining plate 118 and the retaining plate mounting member 116a formed integral with the armature 116 are firmly held together along the entire outer peripheries thereof, the local application of the stressesto the first retaining plate 118 is avoided, but these stresses are distributed all over the retaining plate 118 thereby preventing it from breaking down.

On the other hand, since the portion 1 18a of the first retaining plate 118 is driven in the retaining plate mounting member 116a and then the mounting member 1162 and the retaining plate 118 are bonded together with the epoxy resin 120, the coupling member 

1. In a magnetic clutch comprising a main rotating unit rotated from a driving source, a rotary shaft concentric with said main rotating unit and rotatable independent of said main rotating unit and adapted to be connected to a driven member, an armature mechanically connected to said rotary shaft and placed opposite to said main rotating unit in the axial direction, said armature being movable in the axial direction between a first position where said armature is separated from said main rotating unit by a predetermined distance and a second position where said armature is engaged with said main rotating unit to rotate therewith, and energizeable electromagnetic means for attracting said armature from said first position to said second position when energized, the improvement comprising: a cylindrical elastic material concentric with said rotary shaft and having first and second cylindrical surfaces opposing to each other, first rigid means for mechanically connecting said first cylindrical surface to said armature and second rigid means for mechanically connecting said second cylindrical surface to said rotary shaft, said second rigid means and said second cylindrical surface of said elastic member being axially immovable when said electromagnetic means is energized but said first surface of said elastic member being then axially moved with said first rigid member and said armature when the latter moves to said second position to create thereby in said elastic material an axial elastic strain which is the sole force for returning said armature to said first position when said electromagnetic means is deenergized.
 2. A magnetic clutch according to claim 1, further comprising a plurality of projecting heat radiation members provided on at least one of said first and second means.
 3. A magnetic clutch according to claim 1, further comprising means for preliminarily providing a strain in said elastic material at said first position of said armature so as to produce an elastic force in a direction away from said rotating unit to help maintain said predetermined distance between said armature and main rotating unit while said armature is supposed to be in said first position.
 4. A magnetic clutch according to claim 1 wherein said first means comprises a first retaining plate mechanically connected to said first cylindrical surface of said coupling member, means for mechanically connecting said first retaining plate to said armature and at least one member mounted intermediate to said first retaining plate and said armature so as to provide an air gap therebetween.
 5. In a magnetic clutch comprising a main rotating unit rotated from a driving source, a rotary shaft concentric with said main rotating unit and rotatable independent of said main rotating unit and adapted to be connected to a driven member, an armature mechanically connected to said rotary shaft and placed opposite to said main rotating unit in the axial direction, said armature being movable in the axial direction between a first position where said armature is separated from said main rotating unit by a predetermined distance and a second position where said armature is engaged with said main rotating unit to rotate therewith, and magnetic means for attracting said armature from said first position to said second position, the improvement comprising: a coupling member comprising a cylindrical elastic material concentric with said rotary shaft and having first and second cylindrical surfaces opposing to each other, first means for mechanically connecting said first cylindrical surface to said armature, second means for mechanically connecting said second cylindrical surface to said rotary shaft, said coupling member being subject to an axial elastic strain when said armature is at said second position thereby exerting a force which causes said armature to return to said first position, and means for preliminarily providing a strain in said elastic material at said first position of said armature so as to produce an elastic force in a direction away from said main rotating unit to help maintain said predetermined distance between said armature and main rotating unit while said armature is supposed to be in said first position.
 6. A magnetic clutch according to claim 5, wherein said first means comprises a first retaining plate mechanically connected to said armature and having a cylindrical surface firmly attached to the first cylindrical surface of said coupling member, and said second means comprises a second retaining plate having a portion opposed to said armature in the axial direction and mechanically connected to said rotary shaft and a cylindrical surface firmly attached to the second cylindrical surface of said coupling member, said second retaining plate being provided with said preliminary strain means in the form of a plurality of projections projected towards said armature and being in abutment under pressure with the same at a portion thereof opposing to said armature.
 7. A magnetic clutch according to claim 6, wherein said projections comprise a plurality of pressing members made of an elastic material and securely mounted on said portion of said second retaining plate opposing to said armature.
 8. A magnetic clutch according to claim 5, wherein said first means comprises a first retaining plate having a cylindrical portion formed as an integral part of said armature and concentric with said rotary shaft and the outer periphery firmly attached to the inner surface of said cylindrical portion, and said second means comprises a second retaining plate having a cylindrical portion mechanically connected to said rotary shaft and concentric therewith, said first and second cylindrical surfaces of said coupling member being respectively attached firmly to the inner periphery of said first retaining plate and the outer periphery of said cylindrical portion of said second retaining plate.
 9. A magnetic clutch according to claim 5, wherein said first means comprises a retaining plate mounting member attached to said armature and having a cylindrical retaining plate mounting portion concentric with said rotary shaft and a cylindrical portion adjacent to and around the space between said armature and said main rotating unit and a first cylindrical retaining plate having an outer periphery thereof firmly attached to the inner periphery of said cylindrical retaining plate mounting portion, and said second means comprises a second retaining plate having a cylIndrical portion mechanically connected to said rotary shaft and concentric therewith, said first and second cylindrical surfaces of said coupling member being respectively attached to the inner periphery of said first retaining plate and the outer periphery of said cylindrical portion of said second retaining plate.
 10. A magnetic clutch according to claim 5, further comprising a plurality of projecting heat radiation members provided on at least one of said first and second means.
 11. A magnetic clutch according to claim 5, wherein said first means comprises a first retaining plate mechanically connected to said first cylindrical surface of said coupling member, means for mechanically connecting said first retaining plate to said armature and at least one member mounted intermediate to said first retaining plate and said armature so as to provide an air gap therebetween.
 12. A magnetic clutch according to claim 5, wherein said first means comprises a first retaining plate having a cylindrical portion firmly attached to said first cylindrical surface of said coupling member, means for mechanically connecting said first retaining plate to said armature and at least one member mounted intermediate to said first retaining plate and said armature so as to provide an air gap therebetween; and said second means comprises a second retaining plate having a portion mechanically connected to said rotary shaft, a cylindrical portion firmly attached to the second cylindrical surface of said coupling member and a flange portion radially extending from the circumferential edge of said cylindrical portion and opposing to said coupling member.
 13. A magnetic clutch according to claim 12, wherein said member mounted intermediate to said first retaining plate and said armature is made of an heat insulating material.
 14. A magnetic clutch according to claim 5, wherein said first means comprises a first retaining plate having an annular portion firmly attached to the first cylindrical surface of said coupling member and a flange portion integrally formed on and radially extending from said annular portion, means for mechanically connecting said flange portion to said armature and at least one member mounted intermediate to said flange portion and said armature so as to provide an air gap therebetween; and said second means comprises a second retaining plate having a portion connected to said rotary shaft and a cylindrical portion firmly attached to the second cylindrical surface of said coupling member; said annular portion being formed into a V-shaped section opening towards its center and in cooperation with said cylindrical portion of said second retaining plate so as to radially compress said coupling member at its portions near its opposing sides thereby reducing the heights of said portions.
 15. A magnetic clutch according to claim 14, wherein said member mounted intermediate to said flange portion and said armature is made of a heat insulating material.
 16. In a magnetic clutch comprising a main rotating unit rotated from a driving source, a rotary shaft concentric with said main rotating unit and rotatable independent of said main rotating unit and adapted to be connected to a driven member, an armature mechanically connected to said rotary shaft and placed opposite to said main rotating unit in the axial direction, said armature being movable in the axial direction between a first position where said armature is separated from said main rotating unit by a predetermined distance and a second position where said armature is engaged with said main rotating unit to rotate therewith, and magnetic means for attracting said armature from said first position to said second position, the improvement comprising: a coupling member comprising a cylindrical elastic material concentric with said rotary shaft and having first and second cylindrical surfaces opposing to each other, first means for mechanically connecting said first cylindrical surface to said aRmature, second means for mechanically connecting said second cylindrical surface to said rotary shaft, said coupling member being subjected to an axial elastic strain when said armature is at said second position thereby exerting a force which causes said armature to return to said first position, and wherein said first means comprises a first retaining plate mechanically connected to said first cylindrical surface of said coupling member, means for mechanically connecting said first retaining plate to said armature and at least one member mounted intermediate to said first retaining plate and said armature so as to provide an air gap therebetween. 